Saturday Night Live writer Katie Rich is taking heat after targeting President Donald Trump’s preteen son in an Inauguration Day tweet.

“Barron will be this country’s first homeschool shooter,” Ms. Rich, 33, wrote from her Twitter account Friday amid festivities surrounding Mr. Trump’s swearing-in.

The jab was visible on the writer’s Twitter page for around three hours Friday before Ms. Rich deleted the tweet and set her account to private.

Screenshots of the comment continued to circulate online through Saturday morning, however, spurring condemnation and calls for Ms. Rich’s termination.

“Sick jokes about a 10 year old are classless and go way too far,” opined Twitter user Parker Waters, a self-described photojournalist from New Orleans.

“If you look way, way, up, you can almost see the low road,” Toronto Star columnist Lorrie Goldstein said in a tweet of his own directed toward Ms. Rich.

Barron Trump is not homeschooled, in fact, but attends Columbia Grammar and Preparatory School in New York City. He and his mother, Melania Trump, are expected to stay in Manhattan until his semester ends in the spring.

A petition on Change.org calling for NBC to fire the writer from Saturday Night Live had garnered more than 500 signatures by Saturday morning. Ms. Rich’s Wikipedia page, meanwhile, was briefly vandalized to describe her as a “talentless hack that bullies 10 year olds.”

Efforts to reach NBC for comment Saturday were not immediately successful. The network is slated to air a new episode of SNL late Saturday night.

Mr. Trump has frequently critiqued both NBC and SNL in recent months amid being regularly parodied on the long-running comedy program by actor Alec Baldwin.

“Saturday Night Live is the worst of NBC. Not funny, cast is terrible, always a complete hit job. Really bad television,” Mr. Trump tweeted after last week’s episode.